photovoltaic cell or solar
cell, SEMICONDUCTOR diode that converts light
to electric
current. When light strikes the exposed active surface, it knocks electrons
loose from their sites in the crystal. Some of the electrons have sufficient
energy to cross the DIODE junction and pass through an external circuit. Because
the current and voltage obtained from these devices are small, they are usually
connected in large series-parallel arrays. Practical photovoltaic cells are
currently about 10 to 15% efficient. Although cells constructed from indium
phosphide and gallium arsenide are, in principle, more efficient, silicon-based
cells are generally less costly. Solar cells have long been used to provide
electric power for spacecraft. As costs have decreased, they have seen greater
use as energy sources for irrigation pumps in remote areas, oil drilling platforms,
and mountaintop microwave relay stations, and for small devices such as hand-held
CALCULATORS.

"Photovoltaic power. Appreciation of photovoltaic
power is part of the shift toward an appreciation of the elegance of the solid
state that plants possess. Plants practice photosynthetic solutions to
the problems of power acquisition. Compared to the water
or animal-turned wheels, which are the Ur-metaphors for power production in
the human world, the solid-state quantum-molecular
miracle that involves dropping a photon
of sunlight into a molecular device that will kick out an electron capable of
energetically participating in the life of a cell seems like extravagant science
fiction. Yet this is, in fact, the principle upon which photosynthesis
operates. While the first solid-state devices arrived on the human cultural
frontier in the late 1940's, solid-state engineering had been the preferred
design approach of plants for some two thousand million years. High efficiency
photovoltaics could today meet the daily needs of most people for electricity.
It is the running of basic industries on solar energy that has proved difficult.
Perhaps this is nature's way of telling us that we aspire to too much manufacturing."

samples: "Hives of cyberneticmemories...
vast single organisms, their DNA
coded in silicon..."; "Prepare your minds for a new state of physical scientific
value."; "The total potential here must be nothing less than astronomical!";
"Speed up the synaaaptiiiic floooow."